Use of vanadates as oxidation catalysts

ABSTRACT

Use of a ternary vanadate of formula (I): Fe x  MeI y  MeII z  VO 4  wherein MeI and MeII are different from each other and each stand for an element selected from the group consisting of Y, La, Ce, Pr, Nd, Sm, Er, Gd, Tb, Dy, Ho, Tm, Yb, Lu, Al, Bi and Sb and wherein x=0.05-0.9; y=0.05-0.9; z=0.05-0.9; x+y+z=1, as a catalyst for the oxidation of carbonaceous compounds in combustion engines.

The present invention relates to novel vanadate based catalystcompositions for oxidation of carbonaceous compounds in combustionengines, particularly in diesel engines. These novel catalysts aresuperior over prior art catalysts in view of their thermal stability, aswell as in view of their catalytic efficiency in oxidative reactions,especially in soot oxidation. In the following, the abbreviation “DPF”is employed for the term “diesel particulate filters.”

Such catalyst compositions may be used in diesel engines of mobileapplications such as automotive and non-road applications, but are alsouseable in stationary applications.

BACKGROUND OF THE INVENTION

Caused by their operation characteristics, combustion engines producealong with exhaust gases also a variety of particulates (mostly soot outof the fuel/air mix due to incomplete combustion). Exhaust gases havebeen shown to have a variety of negative effects on public health andnatural environment and several strategies are applied to reduce theirharmfulness, including an SCR (selective catalytic reduction) approach.But since also the emerging particulates are considered harmful, sootcontaining exhaust gases are usually channeled through an appropriatefilter that is able to retain and collect those particulates. However,during operation soot particles accumulate in the filter, leading to anundesirable increase in the back pressure of the exhaust system, therebydecreasing efficiency. To regenerate the filter, soot particles have tobe removed, which can elegantly be realized by their combustion at hightemperatures. One major drawback of this solution is often the limitedtemperature stability of catalytic components inside the filter.

The basic concept of treating exhaust gases of combustion engines withvanadium-based catalysts has been known for a very long time. Forinstance GB 413.744, which was already filed in 1933, discloses the useof vanadium oxide and metallic vanadates as high-temperature catalystsfor the removal of carbon monoxide and other constituents of exhaustgases produced by combustion engines.

Furthermore, the use of vanadium-based catalysts for the catalysis ofreductive treatment of exhaust gases, such as especially selectivecatalytic reduction (SCR) of nitrogen oxides, has also been discussed invarious documents of the prior art.

Thus, WO 2011/127505 discloses vanadium-based SCR catalysts with thegeneral formula XVO₄ (whereas X denotes either Bi, Sb, Ga or Al, aloneor mixtures with transition metals and/or rare earth elements (REE)) incombination with a Ti-based support. In this context also WO 2010/121280is mentionable, as it also discloses catalysts with an XVO₄ composition,wherein X denotes either transition metals or mixtures of transitionmetals with REE, again in combination with a Ti-based support. Suchcatalysts are reported to show enhanced NO_(x) conversion activity andenhanced thermal stability.

DE 102014110937 (Al) discloses vanadate-based SCR-catalysts with thegeneral formula Al_(x)Fe_(y)VO₄ (x+y=1 and x, y>0) that do not containany REE. An exemplary catalyst with a composition ofAl_(0.5)Fe_(0.5)VO₄is therein reported to have better NO_(x) conversionat a certain range of temperatures in comparison to V₂O₅ based catalyst.However, any information about the stability of the describedcomposition in high temperature environment remains undisclosed.

Also catalytic compositions for the use in a filter unit asSCR-catalysts to detoxify exhaust gases of the general formula(A_(x))(T_(y))(R_(z))VO₄ (x+y+z=1 and x,y,z≥0), wherein A is an alkalineearth metal, T is a transition metal and R is an REE are known in priorart and disclosed by e.g. WO 2013/179129 A2.

Also the application of mixtures containing vanadium pentoxide (V₂O₅) asa catalyst for treatment of exhaust gas from diesel engines is known inprior art. For instance, EP 0 154 145 discloses a DPF unit for dieselengines with catalysts comprising V₂O₅ in combination with Li, Na, K,Rb, Cs, Mg, Ca, Sr, Ba, B, Al, Si, Sn, Sb, Bi, Cu, Ag, Zn, Sc, Y, La,Ce, Pr, Nd, Tb, Ti, Zr, Hf, Nb, Cr, Mo, W, Mn, Re, Fe, Co or Ni. Suchcatalysts are supposed to improve ignition and combustion ofparticulates.

Some research data has also been published by Casanova et al., 2013(“Preliminary investigation of bi-functional vanadate-based catalysts inNH₃-SCR and soot combustion reactions”, 11^(th) European congress oncatalysis—Europa Cat-XI, Lyon, France, Sep. 1-6, 2013). In this work aninvestigation of different SCR-catalysts and supports for theirpotential bifunctional application in SCR and regeneration of DPF isdescribed. The publication discloses comparative data for soot oxidationactivity of catalytic compositions comprising Fe_(0.5)Er_(0.5)VO₄ andFeVO₄ in combination with different supports.

M. Casanova has further elaborated on this topic in a presentation heldon Sep. 2, 2013 at the Europa Cat conference in Lyon. According to thispresentation, the combination of SCR and DPF into a single applicationis highly desirable and, while the soot oxidation reaction is notinfluenced by SCR, SCR is clearly influenced by soot oxidation. Whilethis presentation generally mentions ternary vanadates of the formulaFe_((y))Al_((x-y))RE_((1-x))VO₄, where RE stands for a rare earth metal,citing WO 2011/127505, the presentation is silent about the use of anysuch vanadates for oxidative catalysis.

Further prior art documents disclose alkali-vanadates (U.S. Pat. No.4,515,758), cerium-vanadates (EP 1.515.012), silver-vanadates (EP0.077.524), alkaline earth metal-vanadates (EP 1.368.107), as well ascopper-vanadates (U.S. Pat. No. 4,711,870) to be used as catalysts forsoot oxidation. EP 2 878 359 A1 as well as U.S. Pat. No. 4,137,259 A canbe mentioned as additional prior art.

It is the object of the present invention to provide catalystcompositions containing vanadates which are highly effective inoxidative reactions, such as soot oxidation and show an increasedthermal stability.

This object is solved by the use of a ternary vanadate of formula (I)Fe_(x) MeI_(y) MeII_(z) VO₄   (I),

wherein MeI and MeII are different from each other and each stand for anelement selected from the group consisting of Y, La, Ce, Pr, Nd, Sm, Er,Gd, Tb, Dy, Ho, Tm, Yb, Lu, Al, Bi and Sb and wherein

x is 0.05-0.9,

y is 0.05-0.9,

and z is 0.05-0.9

x+y+z=1,

as a catalyst for the oxidation of carbonaceous compounds in combustionengines.

Preferred embodiments of the present invention are disclosed in thedependent claims.

DETAILED DESCRIPTION OF THE INVENTION

Surprisingly it has been discovered that ternary vanadates as definedabove show unexpected positive effects for oxidation of diesel exhaustparticulates in the catalytic oxidation of (diesel) soot.

Specifically, the compounds used according to the present invention showa better catalytic activity (expressed as a lower T₅₀-value) comparedwith state of the art materials e.g. with FeVO₄ or CeVO₄,preferably incomparison to both FeVO₄ and CeVO₄, which may be defined as referencematerials. The T₅₀-value is defined as the temperature at which 50%(w/w) of soot in a mixture containing catalyst and soot is oxidized.

Furthermore, the compounds used according to the present invention alsoshow a better thermal stability compared with aged state of the artmaterials. The term “thermal stability” according to the presentinvention means the catalytic activity characterized by the T₅₀-value ofthe catalyst compositions measured after thermal ageing.

The thermal ageing of the compositions of the present invention isperformed in the range between 700° C. to 850° C./10 h, more preferably750° C.-850° C./10 h , most preferably 800° C.-850° C./10 h.

The thermal stability of these thermally aged compositions of thepresent invention is better compared to e.g. thermally aged FeVO₄ orthermally aged CeVO₄, preferably in comparison to both thermally agedFeVO₄ and thermally aged CeVO_(4,) which may be defined as referencematerials. Better catalytic activity and, especially, better thermalstability allows a safer use in industrial applications and might alsoimprove longevity of the catalysts.

According to the present invention, the ternary vanadates of formula (I)are used in oxidation catalysts. The functioning principle of anoxidation catalyst relies on its capability to catalyze oxidation ofcarbonaceous compounds using oxygen or other oxidizing agents. Thecarbonaceous compounds can be e.g. soot, carbon monoxide, dioxins,methane, NMHC (non-methane hydrocarbons), methanol, NMVOC (non-methanevolatile organic compounds), aromatic hydrocarbons, preferably soot,dioxin and methane, more preferably soot and dioxin and most preferablysoot.

The vanadates used according to the present invention can be prepared assolid-solid solution, physical mixtures and combinations thereof.

For the purpose of the present specification and claims, the term “rareearth element” (REE) means a rare earth element or a mixture thereof, e.g. more than one rare earth element. According to IUPAC a rare earthmetal is an element from the fifteen lanthanides, as well as scandiumand yttrium.

In a preferred embodiment of the present invention in theabove-indicated formula MeI and MeII each stands for an element selectedfrom the group consisting of Y, La, Ce, Pr, Er, Al and Bi. Even morepreferably, MeI and MeII each stands for an element selected from thegroup consisting of Ce, La, Er, Al and Bi.

The present invention also refers to the use of ternary vanadates asoxidation catalysts of general formula Fe_(x) MeI_(y) MeII_(z) VO₄,wherein MeI and MeII are selected from the group of the followingcombinations:

MeI=La, MeII=Er

MeI=Ce, MeII=Al

MeI=Ce, MeII=Bi

MeI=La, MeII=Al

MeI=Er, MeII=Al

MeI=Bi, MeII=Al.

In a further preferred embodiment, in the ternary vanadates of formula(I)

x is 0.1-0.8

y is 0.1-0.8,

z is 0.1-0.8,

x+y+z=1.

In a further preferred embodiment,

x is 0.2-0.6

y is 0.2-0.6

z is 0.2-0.6,

x+y+z=1.

Particularly, in a preferred embodiment of the present invention theternary vanadate used according to the present invention is selectedfrom the group consisting of

Fe_(0.33)Ce_(0.34)Al_(0.33)VO₄

Fe_(0.5)Ce_(0.25)Al_(0.25)VO₄

Fe_(0.33)Ce_(0.34)Bi_(0.33)VO₄

Fe_(0.25)Ce_(0.5)Bi_(0.25)VO₄

Fe_(0.25)Ce_(0.25)Bi_(0.5)VO₄

Fe_(0.5)La_(0.25)Er_(0.25)VO₄

Fe_(0.33)La_(0.34)Al_(0.33)VO₄

Fe_(0.33)Er_(0.34)Al_(0.33)VO₄

Fe_(0.33)Al_(0.33)Bi_(0.34)VO₄.

In a further preferred embodiment of the present invention these ternaryvanadate used according to the present invention exhibit T₅₀ values of450° C. or below, more preferably T₅₀-values of 440° C. or below, mostpreferably T₅₀ of 430° C. or below after calcination at 650° C. for 2hours.

The ternary vanadates employed according to the present invention can beprepared in a manner as known to the skilled artisan, such as from WO2011/127505 A1.

The ternary vanadates employed according to the present invention arepreferably prepared by means of a co-precipitation synthesis. Thestoichiometric amounts of the nitrates of the elements to be included inthe formulation were dissolved in deionized water to yield a mixed metalnitrate solution. Bismuth nitrate hydrate (Bi(NO₃)₃*5 H₂O) representedan exception because not being soluble in water it had to be dissolvedin an acidic solution containing HNO₃. Another aqueous solution wassimultaneously prepared with the stoichiometric amount of ammoniummetavanadate (NH₄VO₃) at 80° C. The two solutions were combined undercontinuous stirring and the pH adjusted by addition of ammonia solution.The precipitate so formed was further stirred, filtered, washed severaltimes with deionized water and dried at 120° C. overnight. The driedmaterial was calcined at 650° C. for 2 hours.

Ternary vanadates can also be synthesized by solid phase reactions orphysical mixtures of vanadates.

In a further preferred embodiment of the present invention the ternaryvanadate according to the present invention is employed in combinationwith a further compound selected from oxides or oxide precursors of Al,Ti, Ce, Zr and mixtures thereof.

The further compound can also be doped (up to 20%) with one or more rareearth elements other than cerium.

Oxide precursors for Al are for example boehmite, aluminium hydroxide,aluminium nitrate, aluminium chloride and others, preferably boehmiteand aluminium hydroxide, most preferably boehmite.

Oxide precursors of Ti are for example: metatitanic acid, titanylsulfate, titanium chloride and others, preferably metatitanic acid.

Oxide precursors of Zr are for example: zirconium hydroxide, zirconylhydroxide, zirconyl nitrate, zirconium nitrate, zirconyl carbonate,zirconium basic carbonate, zirconyl chloride and others, preferablyzirconium hydroxide and zirconyl hydroxide.

Oxide precursors of Ce are for example: cerium hydroxide, ceriumchloride, cerium hydrate, cerium sol, cerium nitrate, cerium carbonate,cerium oxalate, cerium ammonium nitrate and others, preferably ceriumhydroxide, cerium hydrate and cerium sol.

More preferred is the use with this further compound comprising TiO₂ orAl₂O₃ or Ce_(a)Zr_((1-a))O₂, such as Ce_(0.75)Z_(0.25)O₂ or mixturesthereof.

The ratio of the vanadates and the further compound should be between100:0 and 10:90 by weight, more preferably 100:0 and 30:70 by weight andmost preferably 100:0 and 50:50 by weight.

Finally, in yet another aspect of the present invention the ternaryvanadates of formula (I) are used for oxidative exhaust gas catalysis,especially for soot oxidation.

The present invention will now be explained in more detail withreference to examples and comparative examples without being limited tothese. Temperatures indicated are in degree Celsius (° C.).

Synthesis

Example 1—Fe_(0.33)Ce_(0.34)Al_(0.33)VO₄

Fe_(0.33)Ce_(0.34)Al_(0.33)VO₄ was prepared by the co-precipitationmethod. To obtain 3000 mg of powder catalysts, 1847.2 mg of ammoniummetavanadate NH₄VO₃ (AMV) (Sigma Aldrich, Vienna) were dissolved in157.9 g distilled water at 80° C. in order to obtain a 0.1 mol/lsolution; a second solution was prepared by dissolving 2105.2 mg of ironnitrate nonahydrate Fe(NO₃)₃. 9H₂O (Treibacher Industrie AG (TIAG),Althofen), 2331.6 mg of cerium nitrate hexahydrate Ce(NO₃)₃. 6H₂O (TIAG,Althofen) and 1954.7 mg of aluminium nitrate nonahydrate Al(NO₃)₃.9H₂O(Sigma Aldrich, Vienna) in 157.9 g of distilled water. The two solutionswere mixed under continuous stirring and pH was adjusted to 7 with theaddition of aqueous ammonia solution (28 vol %). This caused theprecipitation of a brown compound (Fe_(0.33)Ce_(0.34)Al_(0.33)VO₄) whichwas filtered off, washed several times with distilled water and dried at100° C. overnight and calcined at 650° C. for 2h under air in a mufflefurnace.

Example 2 to 9

The compositions referred to examples 2 to 9 are as disclosed in Tables1A and 1B below and were prepared analogously to the procedure asdisclosed in example 1 but with the different appropriate startingmaterials and amounts. The quantities of the starting materials used forthe preparation according to Examples 2 to 9 are listed in Tables 1A and1B. In case of vanadates containing Bi 0.2 ml of nitric acid were addedto the mixed metal solution.

TABLE 1a Fe(NO₃)₃*9 Al(NO₃)₃*9 Ce(NO₃)₃*6 AMV H₂O H₂O H₂O Ex.Composition [g] [g] [g] [g] 1 Fe_(0.33)Ce_(0.34)Al_(0.33)VO₄ 1.84722.1052 1.9547 2.3316 2 Fe_(0.5)Ce_(0.25)Al_(0.25)VO₄ 1.9000 3.28081.5231 1.7634 3 Fe_(0.33)Ce_(0.34)Bi_(0.33)VO₄ 1.4082 1.6534 1.7251 4Fe_(0.25)Ce_(0.5)Bi_(0.25)VO₄ 1.3965 1.2057 2.5922 5Fe_(0.33)Er_(0.34)Al_(0.33)VO₄ 1.7628 2.0088 1.8652 6Fe_(0.33)La_(0.34)Al_(0.33)VO₄ 1.8524 2.1111 1.9603 7Fe_(0.33)Bi_(0.34)Al_(0.33)VO₄ 1.6454 1.8752 1.7413 8Fe_(0.25)Ce_(0.25)Bi_(0.5)VO₄ 1.3076 1.1290 1.2135 9Fe_(0.5)La_(0.25)Er_(0.25)VO₄ 1.5999 2.7627

TABLE 1b H₂O for H₂O for Er(NO₃)₃*6H₂O Bi(NO₃)₃*5H₂O La(NO₃)₃*6H₂O AMVNitrates Ex. Composition [g] [g] [g] [g] [g] 1Fe_(0.33)Ce_(0.34)Al_(0.33)VO₄ 157.9 157.9 2Fe_(0.5)Ce_(0.25)Al_(0.25)VO₄ 162.4 162.4 3Fe_(0.33)Ce_(0.34)Bi_(0.33)VO₄ 1.9272 120.4 120.4 4Fe_(0.25)Ce_(0.5)Bi_(0.25)VO₄ 1.4479 119.4 119.4 5Fe_(0.33)Er_(0.34)Al_(0.33)VO₄ 2.3635 150.7 150.7 6Fe_(0.33)La_(0.34)Al_(0.33)VO₄ 2.3313 158.4 158.4 7Fe_(0.33)Bi_(0.34)Al_(0.33)VO₄ 2.3198 140.7 140.7 8Fe_(0.25)Ce_(0.25)Bi_(0.5)VO₄ 2.7112 111.8 111.8 9Fe_(0.5)La_(0.25)Er_(0.25)VO₄ 1.5775 1.4806 136.8 136.8

Example 10 Physical Mixture of 0.33 FeVO₄, 0.34 CeVO₄, 0.33Al VO₄

For a physical mixture of single calcined vanadates the net weight ofthe single calcined vanadates were calculated to achieve the finalformal composition Fe_(0.33)Ce_(0.34)Al_(0.33)VO₄. FeVO₄ was prepared asdescribed in comparative example 5. CeVO₄ was prepared as described incomparative example 2. AlVO₄ was prepared in the same manner using2471.9 mg AMV and 211.3 g of distilled water and 7926.3 mg Al(NO₃)₃*9H₂O and 211.3 g of distilled water.

The corresponding mixture was obtained by mixing 890.4 mg of calcinedFeVO₄, 1369.8 mg calcined CeVO₄ and 739.8 mg calcined AlVO₄ in a mortarfor 10 minutes. After mixing no additional calcination was performed.

Example 11 Physical Mixture of 0.25 FeVO₄, 0.5 CeVO₄, 0.25 BiVO₄

For a physical mixture of single calcined vanadates the net weight ofthe single calcined vanadates were calculated to achieve the finalformal composition Fe_(0.25)Ce_(0.5)Bi_(0.25)VO₄. FeVO₄ was prepared asdescribed in comparative example 5. CeVO₄ was prepared as described incomparative example 2. BiVO₄ was prepared in the same manner using1083.0 mg AMV and 92.6 g of distilled water and 4491.6 mg Bi(NO₃)₃*5H₂O,0.2 ml of nitric acid and 92.6 g of distilled water.

The corresponding mixture was obtained by mixing 509.9 mg of calcinedFeVO₄, 1523.0 mg calcined CeVO₄ and 967.1 mg calcined BiVO₄ in a mortarfor 10 minutes. After mixing no additional calcination was performed.

Comparative Example 1—Ce_(0.5)Al_(0.5)VO₄

Ce_(0.5)Al_(0.5)VO₄ was prepared by the co-precipitation method. Toobtain 3000 mg of powder catalysts, 1767.4 mg of ammonium metavanadateNH₄VO₃ (Aldrich) were dissolved in 151.1 g of distilled water at 80° C.in order to obtain a 0.1 mol/l solution; a second solution was preparedby dissolving 2833.7 mg of aluminium nitrate nonahydrate Al(NO₃)₃. 9H₂O(Aldrich) and 3280.6 mg of cerium nitrate hexahydrate Ce(NO₃)₃. 6H₂O(Treibacher) in 151.1 g of distilled water at 80° C. The two solutionswere mixed under continuous stiffing and pH was adjusted to 7 with theaddition of aqueous ammonia solution (28 vol %). This caused theprecipitation of a light brown compound (Ce_(0.5)Al_(0.5)VO₄) which wasfiltered off, washed several times with distilled water, dried at 100°C. overnight and calcined at 650° C. for 2h under air in a mufflefurnace.

Comparative Example 2 to 6

The compositions referred to as comparative examples 2 to 6 aredisclosed in Tables 2A and 2B below and were prepared analogously to theprocedure as disclosed in comparative example 1 but using appropriatestarting material and amounts. The quantities of the starting materialsused for the preparation according to comparative examples 2 to 6 are aslisted in

Tables 2A and 2B. In case of vanadates containing Bi 0.2 ml of nitricacid were added to the mixed metal solution.

TABLE 2A Fe(NO₃)₃*9 Al(NO₃)₃*9 Ce(NO₃)₃*6 Comp. AMV H₂O H₂O H₂O Ex.Composition [g] [g] [g] [g] 1 Ce_(0.5)Al_(0.5)VO₄ 1.7674 2.8337 3.2806 2CeVO₄ 1.3754 5.1061 3 Er_(0.5)La_(0.5)VO₄ 1.3089 4 Fe_(0.5)Al_(0.5)VO₄2.2453 3.8772 3.6001 5 FeVO₄ 2.0540 7.0937 6 Fe_(0.3)La_(0.7)VO₄ 1.53241.5876

TABLE 2B H₂O for H₂O for Comp. Er(NO₃)₃*6H₂O Bi(NO₃)₃*5H₂O La(NO₃)₃*6H₂OAMV Nitrates Ex. Composition [g] [g] [g] [g] [g] 1 Ce_(0.5)Al_(0.5)VO₄151.1 151.1 2 CeVO₄ 117.6 117.6 3 Er_(0.5)La_(0.5)VO₄ 2.5814 2.4227111.9 111.9 4 Fe_(0.5)Al_(0.5)VO₄ 191.9 191.9 5 FeVO₄ 175.6 175.6 6Fe_(0.3)La_(0.7)VO₄ 3.9710 131.0 131.0

Comparative Example 7-8.4% FeVO₄/ 91.6% DT 58

Mixture made by slurry synthesis 8.4 wt. % FeVO₄/DT-58 (TiO₂/SiO₂/WO₃81/10/9 weight %) purchased from Cristal, Thann)

To obtain 3000 mg of catalyst, 252 mg of FeVO₄ (prepared as described incomparative example 5) and 2748 mg of DT-58 (TiO₂/SiO₂/WO₃ (81/10/9weight %) from Cristal) were mixed in distilled water under continuousstirring at ca. 100° C. After slow evaporation of water a wet cake wasobtained. The catalyst was obtained after calcination at 650° C./2h.

Comparative Example 8-50% FeVO₄/50% DT 58

Mixture made by slurry synthesis 50 wt. % FeVO₄/DT-58

To obtain 3000 mg of catalyst, 1500 mg of FeVO₄ (prepared as describedin comparative example 5) and 1500 mg of DT-58 (TiO₂/SiO₂/WO₃ (81/10/9weight %) purchased from Cristal, Thann) were mixed in distilled waterunder continuously stiffing at ca. 100° C. After slow evaporation ofwater a wet cake was obtained. The catalyst was obtained aftercalcination at 650° C./2h.

Comparative Example 9—Physical Mixture of 0.3 FeVO₄, 0.7 LaVO₄

For a physical mixture of single calcined vanadates the net weight ofthe single calcined vanadates were calculated to achieve the finalformal composition Fe_(0.3)La_(0.7)VO₄. FeVO₄ was prepared as describedin comparative example 5. LaVO₄ was prepared in the same manner using1382.0 mg AMV and 118.1 g of distilled water and 5116.0 mg lanthanumnitrate hexahydrate La(NO₃)₃*6H₂O and 118.1 g of distilled water.

The corresponding mixture was obtained by mixing 671.4 mg of calcinedFeVO₄ and 2328.6 mg calcined LaVO₄ in a mortar for 10 minutes. Aftermixing no additional calcination was performed.

Conditions for Catalytic Powder Testing

Sample Preparation and Thermal Ageing

The synthesized and calcined (650° C./2h) vanadates of the presentinvention were milled manually in an agate mortar. Powdered samples andcarbon black (CB, Printex U) (Evonik Degussa GmbH, Essen) were carefullymixed in an agate mortar in a mass ratio of 20:1 for ten minutes untilthe mixture was homogeneous to result in a tight contact mode.

Optionally thermal ageing was employed to the powdered samples prior tomixing with carbon black. Ageing of samples was performed for 10 hoursin a conventional muffle oven with a heating rate of 10° C./min ateither 800° C. or 850° C. as indicated in table 3 below.

Measurement of the Catalytic Activity

Soot oxidation activity was determined by thermogravimetry analysis(TGA) (Q500, TA Instruments) under ambient atmosphere. Each sample(soot+catalyst, ca. 20 mg) was placed in a small flat Pt crucible andthe total gas flow was set to 60 ml/min. The samples were pretreated for1 h at 120° C. in order to desorb water. The soot combustion activitiesof the catalysts were measured under dynamic conditions with a heatingramp of 10° C./min in a temperature range of from 25° C. to 800° C. Thetemperature at which 50% of weight loss is observed (T₅₀, correspondingto removal of 50% of soot) was used as a measure of catalytic activity.

The results of catalytic activity tests performed with the compoundsobtained according to the examples above with or without previousthermal ageing are summarized in the following table:

TABLE 3 T₅₀ [° C.] T₅₀ [° C.] (calcined (calcined T₅₀ [° C.] 650° C./2h + 650° C./2 h + (calcined aged 800° aged 850° Sample Composition 650°C./2 h) C./10 h) C./10 h) Example 1 Fe_(0.33)Ce_(0.34)Al_(0.33)VO₄ 431421 399 Example 2 Fe_(0.5)Ce_(0.25)Al_(0.25)VO₄ 434 Example 3Fe_(0.33)Ce_(0.34)Bi_(0.33)VO₄ 417 Example 4Fe_(0.25)Ce_(0.5)Bi_(0.25)VO₄ 400 Example 5Fe_(0.33)Er_(0.34)Al_(0.33)VO₄ 422 406 399 Example 6Fe_(0.33)La_(0.34)Al_(0.33)VO₄ 434 409 Example 7Fe_(0.33)Bi_(0.34)Al_(0.33)VO₄ 418 Example 8Fe_(0.25)Ce_(0.25)Bi_(0.5)VO₄ 412 Example 9Fe_(0.5)La_(0.25)Er_(0.25)VO₄ 437 Example 10Fe_(0.33)Ce_(0.34)Al_(0.33)VO₄*) 439 Example 11Fe_(0.25)Ce_(0.5)Bi_(0.25)VO₄*) 419 Comparative Ce_(0.5)Al_(0.5)VO₄ 465Example 1 Comparative CeVO₄ 487 Example 2 ComparativeEr_(0.5)La_(0.5)VO₄ 519 Example 3 Comparative Fe_(0.5)Al_(0.5)VO₄ 463Example 4 Comparative FeVO₄ 452 437 464 Example 5 ComparativeFe_(0.3)La_(0.7)VO₄ 456 Example 6 Comparative FeVO₄ (8.4%)/DT-58**) 520Example 7 Comparative FeVO₄ (50%)/DT-58**) 474 Example 8 ComparativeFe_(0.3)La_(0.7)VO₄*) 485 Example 9 *)made via physical mixture withoutcalcination of the final product (educts were calcined) **)DT-58 =TiO₂/SiO₂/WO₃ (81/10/9 weight %)

The invention claimed is:
 1. Use A method of catalytically oxidizingcarbonaceous compounds from a combustion engine, comprising: contactinga catalyst comprising a ternary vanadate of formula (I) withcarbonaceous compounds from the combustion engine:Fe_(x) MeI_(y) MeII_(z) VO₄   (I), wherein MeI and MeII are differentfrom each other and each stand for an element selected from the groupconsisting of Y, La, Ce, Pr, Nd, Sm, Er, Gd, Tb, Dy, Ho, Tm, Yb, Lu, Al,Bi and Sb and wherein x=0.05-0.9 y=0.05-0.9 z=0.05-0.9 x+y+z=1, thecatalyst catalysing oxidation of the carbonaceous compounds from thecombustion engine.
 2. The method according to claim 1, wherein MeI andMeII each stand for an element selected from the group consisting of Y,La, Ce, Pr, Er, Al, Bi.
 3. The method according to claim 1, that whereinMeI and MeII each stand for an element selected from the groupconsisting of Ce, La, Er, Al and Bi.
 4. The method according to claims 1to 3, characterized in wherein MeI and MeII are selected from the groupof the following combinations: MeI=La, MeII=Er, MeI=Ce, MeII=Al, MeI=Ce,MeII=Bi, MeI=La, MeII=Al, MeI=Er, MeII=Al, and MeI=Bi, MeII=Al.
 5. Themethod according to claims 1, wherein x=0.1-0.8 y=0.1-0.8 z=0.1-0.8x+y+z=1.
 6. The method according to claim 5, wherein x=0.2-0.6 y=0.2-0.6z=0.2-0.6 x+y+z=1.
 7. The method according to claim 1 wherein theternary vanadate is selected from the group consisting of:Fe_(0.33)Ce_(0.34)Al_(0.33)VO₄, Fe_(0.5)Ce_(0.25)Al_(0.25)VO₄,Fe_(0.33)Ce_(0.34)Bi_(0.33)VO₄, Fe_(0.25)Ce_(0.5)Bi_(0.25)VO₄,Fe_(0.25)Ce_(0.25)Bi_(0.5)VO₄, Fe_(0.5)La_(0.25)Er_(0.25)V₄,Fe_(0.33)La_(0.34)Al_(0.33)V_(O4,) Fe_(0.33)Er_(0.34)Al_(0.33)V_(O4),and Fe_(0.33)Al_(0.33)Bi_(0.34)V_(O4).
 8. The method according to claim1, wherein the ternary vanadate is employed in combination with anothercompound selected from oxides, oxide precursors of Al, Ti, Ce, Zr, andmixtures thereof.
 9. A method of catalytically oxidizing exhaust gasfrom a combustion engine, comprising: contacting a catalyst comprising aternary vanadate of formula (I) with exhaust gas from the combustionengine:Fe_(x) MeI_(y) MeII_(z) VO₄   (I), wherein MeI and MeII are differentfrom each other and each stand for an element selected from the groupconsisting of Y, La, Ce, Pr, Nd, Sm, Er, Gd, Tb, Dy, Ho, Tm, Yb, Lu, Al,Bi and Sb and wherein x=0.05-0.9 y=0.05-0.9 z=0.05-0.9 x+y+z=1, thecatalyst promoting oxidation of the exhaust gas from the combustionengine.
 10. The method according to claim 9, the catalyst promotingoxidation of soot in the exhaust gas.